It is well known that sample imaging can be performed using local magnetic fields. The state of the art in imaging using local magnetic fields, however, still experiences several drawbacks. Some imaging apparatus suffer from relatively poor field sensitivity such as the scanning Hall probe microscope. While others, such as existing scanning SQUID microscopes, have relatively poor spatial resolution. Superconducting quantum interference devices (SQUIDs) are more fully explained, for example, in the article by John Clarke in the August 1994 issue of Scientific American which is herein incorporated by reference.
In addition to the above drawbacks, existing scanning Hall probe microscopes have limited scan ranges and existing SQUID microscopes are very complex mechanically.
Furthermore, among existing scanning devices, piezoelectric scanners have the disadvantage that they have limited scan range, especially at low temperatures. Conventional piezoelectric inchworms have reasonable resolution over large scan ranges, but require large, rapidly changing voltages to drive them, and do not work at extreme sample temperatures. And, in remote mechanical scanning, long mechanical connections are required between the drive mechanism and the sample mount as in, for example, cryogenic applications. Such long mechanical connections tend to limit the mechanical stiffness that can be designed into the system, making it more sensitive to vibrations.
In the field of scanning microscopes, U.S. Pat. No. 4,874,945 is directed to a structure that combines a scanning or transmission electron microscope with a tunneling microscope. The '945 Patent employs a mechanism for coarse positioning of the piezo scanner. The coarse positioning mechanism is designed to be firmly locked in position while scanning takes place using the piezo mechanism. The '945 mechanism has several drawbacks including its complexity and its lack of flexibility for performing large field-of-view scanning.